Grafted isotactic polypropylene obtained by metallocene catalysis

ABSTRACT

The present invention relates to an isotactic polypropylene obtained by metallocene catalysis, onto which is grafted a functional monomer. 
     The invention also relates to a composition which may form part of the composition of a coextrusion binder. This composition according to the invention comprises isotactic polypropylene obtained by metallocene catalysis, grafted and then optionally diluted with at least one polyolefin (C1) and/or in at least one polymer of elastomeric nature (D). 
     The invention also relates to a multilayer structure comprising a layer (L) comprising the above binder, and, directly attached thereto, a layer (E):
         which is polar, nitrogenous or oxygenated, such as a layer of polyamide resin, of ethylene/saponified vinyl acetate copolymer (EVOH) or of polyester; or   of a mineral oxide deposited on a polymer such as polyethylene (PE), polyethylene terephthalate (PET) or EVOH; or   which is metallic or metalloplastic.

This is a divisional application of application Ser. No. 10/208,192,filed Jul. 31, 2002, now U.S. Pat. No. 6,750,288 B2 issued, Jun. 15,2004 claiming priority of French application No. 0110252 filed Jul. 31,2001.

The present invention relates to an isotactic polypropylene obtained bymetallocene catalysis, onto which is grafted a functionalised monomer,and also to a composition comprising such a polymer. The invention alsorelates to a multilayer structure, at least one of the layers of whichcomprises isotactic polypropylene obtained by metallocene catalysis inits composition.

The isotactic polypropylene obtained by metallocene catalysis andgrafted with a functionalised monomer may form part of the compositionof a coextrusion binder. The coextrusion binder comprises isotacticpolypropylene obtained by metallocene catalysis, grafted and thenoptionally diluted in at least one polyolefin (C1) and/or in at leastone polymer of elastomeric nature (D).

These coextrusion binders are useful, for example, for manufacturingmultilayer materials for wrapping. Mention may be made of materialscomprising a polyamide (PA) film and a polypropylene (PP) film, thepolypropylene film possibly being laminated over the polyamide film orcoextruded with the polyamide. The coextrusion binder is arrangedbetween the polypropylene film and the polyamide film for good adhesionof the two films. These multilayer materials may be, for example:

-   -   three-layer structures of the type such as, for example,        PP/binder/EVOH in which EVOH denotes a copolymer of ethylene and        of vinyl alcohol, or an ethylene/partially or totally saponified        vinyl acetate copolymer, the binder layer being sandwiched        between an EVOH layer and a PP layer, or    -   five-layer structures of the type such as, for example,        PP/binder/EVOH/binder/PP, in which the EVOH layer is sandwiched        between two layers of binders, each of them being sandwiched        between the EVOH layer and a PP layer.

The grafted polymer according to the invention may also be useful as acompatibilizer, for example in blends of polyamide and polypropylene orin blends of polypropylene and glass fibres.

Polypropylene is described in Kirk-Othmer, Encyclopedia of ChemicalTechnology, 4th edition, Vol. 17, pages 784-819, John Wiley & Sons,1996. Almost all of the polypropylene sold consists essentially ofisotactic polypropylene obtained by Ziegler-Natta catalysis, possiblycontaining a small amount of atactic polypropylene.

Extensive prior art exists describing grafted polypropylene, but this isalways isotactic polypropylene obtained by Ziegler-Natta catalysis,abbreviated as zniPP in the text hereinbelow.

Document U.S. Pat. No. 5,235,149 describes wrappings closed with capsconsisting of an aluminium foil, a binder layer and a polypropylenelayer. The binder layer of the cap consists of various polymers graftedwith acrylic acid or maleic anhydride, and the polymers may be chosenfrom polyethylene, polypropylene, copolymers of ethylene and of vinylacetate and copolymers of ethylene and of methyl acrylate.

Documents DE 19 535 915 A and EP 689 505 describe a graftedpolypropylene block copolymer for adhesively binding polypropylene filmsto metal sheets.

Document EP 658 139 describes structures similar to those describedabove, but the binder is a grafted random polypropylene copolymercomprising from 1 to 10% comonomer, the Mw/Mn ratio being between 2 and10 and the MFI (melt flow index) is between 1 and 20/10 min (at 230° C.under 2.16 kg).

The free-radical grafting of functionalised monomers onto thepolyolefins is performed either in the melt-or in solution usingfree-radical initiators, for instance peroxides, or in the solid stateby irradiation. Under the action of the radicals, side reactions takeplace at the same time as the grafting reaction. They lead to anincrease in the molecular mass in the case where the polymer to begrafted is polyethylene, or to a decrease in the molecular mass in thecase where it is polypropylene. If the amount of free radicals requiredfor the grafting reaction is large, the change in the molecular mass ofthe polyolefin leads to a large change in its melt viscosity. Thisgrafting generally takes place in an extruder. The viscosity of thegrafted polyethylene is then so high that it can no longer be extruded,whereas the viscosity of the grafted polypropylene is so low that itcannot be extruded either. These phenomena make it necessary to reducethe amount of reactive functions that may be incorporated into thepolyolefin by free-radical grafting of functional monomers.

In the case of mixtures of virtually equivalent amounts of polyethyleneand of polypropylene to be grafted by free-radical grafting with largeamounts of functionalised monomers, as is the case in document EP 802207, the increase in the molecular mass of the grafted polyethylene iscompensated for by the decrease in the molecular mass of the graftedpolypropylene.

It has now been found that a functionalised monomer can be grafted inlarge amount onto isotactic polypropylene obtained by metallocenecatalysis (miPP) and that the melt flow index of the grafted miPPobtained is lower than in the case of the grafted isotacticpolypropylene obtained by Ziegler-Natta catalysis (zniPP), thus makingthe grafted miPP or compositions comprising it easier to extrude.

Furthermore, it has been found that grafted miPP is advantageous interms of application compared with the polypropylenes obtained byZiegler-Natta catalysis during its use in coextrusion binders.

One subject of the invention is a composition comprising:

-   -   10% to 100% by weight of isotactic polypropylene homopolymer or        copolymer obtained by metallocene catalysis (miPP);    -   0% to 90% by weight of polyethylene (A) homopolymer or        copolymer;    -   0% to 90% by weight of polymer (B) chosen from isotactic        polypropylene homopolymer or copolymer obtained by Ziegler-Natta        catalysis (B1), poly-(1-butene) homopolymer or copolymer (B2),        polystyrene homopolymer or copolymer (B3), a blend of (B1) and        (B2), a blend of (B1) and (B3), a blend of (B2) and (B3) and a        blend of (B1), (B2) and (B3); the percentages being based on the        total weight of the isotactic polymer (miPP) and any polymer (A)        and polymer (B); and,        the said polymer or polymers being grafted with a functional        monomer.

According to one embodiment of the composition, the functionalisedmonomer is unsaturated and non-aromatic. The term “functionalisedmonomer” means a monomer comprising at least one chemical function.

According to one embodiment of the composition, the functionalisedmonomer is taken from the group comprising alkoxysilanes, carboxylicacids and derivatives thereof, acid chlorides, isocyanates, oxazolines,epoxides, amines and hydroxides.

According to one embodiment of the composition, the functionalisedmonomer is maleic anhydride.

According to one embodiment of the composition, at least one comonomerof polyethylene (A) copolymer is chosen from α-olefins containing from 3to 30 carbon atoms, esters of unsaturated carboxylic acids, vinyl estersof saturated carboxylic acids, unsaturated epoxides, alicyclic glycidylesters and ethers, unsaturated carboxylic acids, salts thereof,anhydrides thereof and dienes.

According to one embodiment of the composition, the polyethylene (A) ischosen from LDPE, HDPE, LLDPE, VLDPE, PE obtained by metallocenecatalysis, EPR and EPDM elastomers and blends thereof, ethylene/alkyl(meth)acrylate copolymers, ethylene/alkyl (meth)acrylate/maleicanhydride copolymers and ethylene/vinyl acetate/maleic anhydridecopolymers.

According to one embodiment of the composition, it is diluted in apolyolefin (C1) and/or a polymer of elastomeric nature (D).

According to one embodiment of the composition, the amount of polyolefin(C1) and/or of polymer of elastomeric nature (D) is advantageously from20 to 1 000 and preferably from 30 to 500 parts by weight per 10 partsof grafted isotactic polypropylene obtained by metallocene catalysis.

According to one embodiment of the composition, the proportions ofpolyolefin (C1) and of polymer of elastomeric nature (D) are such thatthe ratio (D)/(C1) is between 0 and 1 and more particularly between 0and 0.5.

According to one embodiment of the composition, it is included in acoextrusion binder.

A subject of the invention is also a multilayer structure comprising alayer (L) comprising a composition as described above and, directlyattached to the said layer (L), a layer (E):

-   -   which is polar, nitrogenous or oxygenated, such as a layer of        polyamide resin, of ethylene/saponified vinyl acetate (EVOH)        copolymer or of polyester; or    -   of a mineral oxide deposited on a polymer such as PE,        polyethylene terephthalate (PET) or EVOH; or    -   which is metallic or metalloplastic.

According to one embodiment of the structure, it comprises apolyolefin-based layer (F) directly attached to the layer (L), the layer(L) thus being sandwiched between the said layer (F) and the layer (E).

The composition based on isotactic polypropylene obtained by metallocenecatalysis (miPP) optionally comprises a polymer (A) denoting apolyethylene homopolymer or copolymer and/or a polymer (B) chosen fromisotactic polypropylene homopolymer or copolymer (B1), poly-1-butenehomopolymer or copolymer (B2), polystyrene homopolymer or copolymer(B3), a blend of (B1) and (B2), a blend of (B2) and (B3), a blend of(B1) and (B3) and a blend of (B1), (B2) and (B3). This means that ablend is grafted which comprises either miPP without polymer (A) andwithout polymer (B), or miPP and polymer (A), or miPP and polymer (B),or alternatively miPP, polymer (A) and polymer (B). Advantageously, theproportion of polymers (A) and/or (B) represents less than 40% by weightof the combination of the miPP and the polymer (A) and/or the polymer(B).

The isotactic polypropylene obtained by metallocene catalysis,abbreviated hereinbelow as miPP, and the systems for synthesizing it areknown and described in the following references from the Applicant: U.S.Pat. No. 6,214,949; U.S. Pat. No. 5,968,854; EP 856 525; U.S. Pat. No.5,789,502; EP 849 286; EP 802 206; U.S. Pat. No. 5,561,092; EP 581 754.

The isotactic polypropylene obtained by metallocene catalysis (miPP) is,according to the above references, a polymer comprising from 0% to 10%by weight of a comonomer or a blend of comonomers chosen from ethylene,butene, isobutylene and 4-methylpentene.

As regards the polymer (A), it is chosen from polyethylene homopolymersor copolymers.

Comonomers that may be mentioned include:

-   -   α-olefins, advantageously those containing from 3 to 30 carbon        atoms. Examples of α-olefins containing from 3 to 30 carbon        atoms as possible comonomers comprise propylene, 1-butene,        1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene,        3-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene,        1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene,        1-dococene, 1-tetracocene, 1-hexacocene, 1-octacocene and        1-triacontene. These α-olefins may be used alone or as a blend        of two or more than two.    -   esters of unsaturated carboxylic acids such as, for example,        alkyl (meth)acrylates, the alkyls possibly containing up to 24        carbon atoms. Examples of alkyl acrylates or methacrylates are        especially methyl methacrylate, ethyl acrylate, n-butyl        acrylate, isobutyl acrylate and 2-ethylhexyl acrylate.    -   vinyl esters of saturated carboxylic acids such as, for example,        vinyl acetate or propionate.    -   unsaturated epoxides. Examples of unsaturated epoxides are,        especially: aliphatic glycidyl esters and ethers such as allyl        glycidyl ether, vinyl glycidyl ether, glycidyl maleate and        itaconate, glycidyl acrylate and methacrylate, and alicyclic        glycidyl esters and ethers such as 2-cyclo-hexene-1-glycidyl        ether, cyclohexene-4,5-diglycidyl carboxylate,        cyclohexene-4-glycidyl carboxylate,        5-norbornene-2-methyl-2-glycidyl carboxylate and        endocis-bicyclo[2.2.1]-5-heptene-2,3-diglycidyl dicarboxylate.    -   unsaturated carboxylic acids, salts thereof and anhydrides        thereof. Examples of anhydrides of unsaturated dicarboxylic acid        are especially maleic anhydride, itaconic anhydride, citraconic        anhydride and tetrahydrophthalic anhydride.    -   dienes such as, for example, 1,4-hexadiene.

The polymer (A) may comprise several comonomers.

Advantageously, the polymer (A), which may be a blend of severalpolymers, comprises at least 50 mol % and preferably 75 mol % ofethylene. The density of (A) may be between 0.86 and 0.98 g/cm³. The MFI(viscosity index at 190° C., under 2.16 kg) is advantageously between 1and 1 000 g/10 min.

Examples of polymers (A) that may be mentioned include:

-   -   low density polyethylene (LDPE)    -   high density polyethylene (HDPE)    -   linear low density polyethylene (LLDPE)    -   very low density polyethylene (VLDPE)    -   the polyethylene obtained by metallocene catalysis, i.e. the        polymers obtained by copolymerization of ethylene and of        α-olefin such as propylene, butene, hexene or octene in the        presence of a single-site catalyst generally consisting of one        zirconium or titanium atom and of two cyclic alkyl molecules        linked to the metal. More specifically, metallocene catalysts        are usually composed of two cyclopentadiene rings linked to the        metal. These catalysts are frequently used with aluminoxanes as        co-catalysts or activators, preferably methylaluminoxane (MAO).        Hafnium may also be used as the metal to which the        cyclopentadiene is attached. Other metallocenes may include        transition metals from Groups IV A, V A and VI A. Metals of the        lanthamide series may also be used.    -   EPR (ethylene-propylene-rubber) elastomers;    -   EPDM (ethylene-propylene-diene) elastomers;    -   blends of polyethylene with an EPR or an EPDM;    -   ethylene/alkyl (meth)acrylate copolymers possibly containing up        to 60% by weight of alkyl (meth)acrylate and preferably from 2%        to 40%;    -   ethylene/alkyl (meth)acrylate/maleic anhydride copolymers        obtained by copolymerization of the three monomers, the        proportions of alkyl (meth)acrylate being those of the above        copolymers, the amount of maleic anhydride being from 0% to 10%        and preferably from 0.2% to 6% by weight.    -   ethylene/vinyl acetate/maleic anhydride copolymers obtained by        copolymerization of the three monomers, the proportions of vinyl        acetate being the same as those of the alkyl (meth)acrylate in        the above copolymers and the proportions of MAH being the same        as those of the above copolymers.

As regards the polymer (B1), this is an isotactic polypropylenehomopolymer or copolymer obtained by Ziegler-Natta catalysis (zniPP).Comonomers that may be mentioned include:

-   -   α-olefins, advantageously those containing from 3 to 30 carbon        atoms. Examples of such α-olefins are the same as for (A) except        for the replacement of propylene with ethylene in the list,    -   dienes.

The polymer (B1) may also be a copolymer containing polypropyleneblocks.

Examples of polymers (B1) that may be mentioned include:

-   -   polypropylene    -   blends of polypropylene and of EPDM or EPR.

Advantageously, the polymer (B1) which may be a blend of severalpolymers, comprises at least 50 mol % and preferably 75 mol % ofpropylene.

As regards the polymer (B2), it is chosen from poly(1-butene) andcopolymers of 1-butene with ethylene and another α-olefin containingfrom 3 to 10 carbon atoms, except for the propylene (B1) alreadymentioned.

As regards the polymer (B3), it is chosen from polystyrene and styrenecopolymers. Among the copolymers, examples that may be mentioned aredienes containing from 4 to 8 carbon atoms.

As regards the functionalised monomer, it is unsaturated andnon-aromatic. Examples that may be mentioned include alkoxysilanes,carboxylic acids and derivatives thereof, acid chlorides, isocyanates,oxazolines, epoxides, amines and hydroxides.

Among the alkoxysilanes bearing an unsaturation, mention may be made of:

-   -   vinyltrialkoxysilanes CH₂═CH—Si(OR)₃;    -   allyltrialkoxysilanes CH₂═CH—CH₂—Si (OR)₃;    -   (meth)acryloxyalkyltrialkoxysilanes (or (meth)acrylsilanes)    -   CH₂═CR₁—CO—O—Y—Si(OR)₃ in which: R is an alkyl containing from 1        to 5 carbon atoms or an alkoxy —R₂OR₃ in which R₂ and R₃ are        alkyls containing not more than 5 carbon atoms for the        combination R₂ and R₃; R₁ is a hydrogen or a methyl; Y is an        alkylene containing from 1 to 5 carbon atoms.

Vinylsilanes such as trimethoxyvinylsilane, triethyloxyvinylsilane,tripropoxyvinylsilane, tributoxyvinylsilane, tripentoxyvinylsilane ortris(β-methoxyethoxy) vinylsilane, allylsilanes such astrimethoxyallylsilane, triethoxyallylsilane, tripropoxyallylsilane,tributoxyallylsilane or tripentoxyallylsilane, acrylsilanes such asacryloxymethyltrimethoxysilane, methacryloxymethyl-methoxysilane,acryloxyethyltrimethoxysilane, methacryloxymethylmethoxysilane,acryloxyethyltrimethoxysilane, methacryloxyethyl-trimethoxysilane,acryloxypropyltrimethoxysilane, methacryloxypropyltrimethoxysilane,acryloxybutyl-trimethoxysilane, methacryloxybutylmethoxysilane,acryloxyethyltriethoxysilane, methacryloxyethyl-triethoxysilane,methacryloxyethyltripropoxysilane, acryloxypropyltributoxysilane ormethacryloxypropyl-tripentoxysilane are used, for example.

It is also possible to use blends of these products. The following arepreferably used:

-   -   vinyltrimethoxysilane (VTMO) CH₂═CH—Si—(OCH₃)₃;    -   vinyltriethoxysilane (VTEO) CH₂═CH—Si—(OCH₂CH₃)₃;    -   vinyltrimethoxyethoxysilane (VTMOEO) CH₂═CH—Si—(OCH₂OCH₂CH₃)₃;        and    -   (3-(methacryloxy)propyl)trimethoxysilane        CH₂═C(CH₃)—C(O)O—(CH₂)₃—Si (OCH₃)₃.

Examples of unsaturated carboxylic acids are those containing from 2 to20 carbon atoms such as acrylic acid, methacrylic acid, maleic acid,fumaric acid and itaconic acid. The functional derivatives of theseacids comprise, for example, anhydrides, ester derivatives, amidederivatives, imide derivatives and metal salts (such as alkali metalsalts) of unsaturated carboxylic acids.

Unsaturated dicarboxylic acids containing from 4 to 10 carbon atoms andfunctional derivatives thereof, particularly anhydrides thereof, aregrafting monomers that are particularly preferred.

These grafting monomers comprise, for example, maleic acid, fumaricacid, itaconic acid, citraconic acid, allylsuccinic acid,cyclohex-4-ene-1,2-dicarboxylic acid,4-methylcyclohex-4-ene-1,2-dicarboxylic acid,bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid,x-methylbicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid, maleicanhydride, itaconic anhydride, citraconic anhydride, allylsuccinicanhydride, cyclohex-4-ene-1,2-dicarboxylic anhydride,4-methylenecyclohex-4-ene-1,2-dicarboxylic anhydride,bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride andx-methylbicyclo[2.2.1]hept-5-ene-2,2-dicarboxylic anhydride.

Examples of other grafting monomers comprise C1-C8 alkyl esters orglycidyl ester derivatives of unsaturated carboxylic acids, such asmethyl acrylate, methyl methacrylate, ethyl acrylate, ethylmethacrylate, butyl acrylate, butyl methacrylate, glycidyl acrylate,glycidyl methacrylate, monoethyl maleate, diethyl maleate, monomethylfumarate, dimethyl fumarate, monomethyl itaconate and diethyl itaconate;amide derivatives of unsaturated carboxylic acids such as acrylamide,methacrylamide, maleic monoamide, maleic diamide, maleicN-monoethylamide, maleic N,N-diethylamide, maleic N-monobutylamide,maleic N,N-dibutylamide, fumaric monoamide, fumaric diamide, fumaricN-monoethylamide, fumaric N,N-diethylamide, fumaric N-monobutylamide andfumaric N,N-dibutylamide; imide derivatives of unsaturated carboxylicacids such as maleimide, N-butylmaleimide and N-phenylmaleimide; andmetal salts of unsaturated carboxylic acids such as sodium acrylate,sodium methacrylate, potassium acrylate and potassium methacrylate.

Various known processes may be used to graft the miPP compositionoptionally comprising (A) and/or (B) with a grafting monomer.

For example, the grafting may be performed by heating this compositionto a high temperature, about 150° C. to about 300° C., in the presenceor absence of a solvent with or without free-radical initiator.

Suitable solvents that may be used in this reaction are benzene,toluene, xylene, chlorobenzene and cumene, inter alia.

Suitable free-radical initiators that may be used comprise t-butylhydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide-,di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide,1,3-bis(t-butylperoxyisopropyl)benzene, acetyl peroxide, benzoylperoxide, isobutyryl peroxide, bis(3,5,5-trimethylhexanoyl) peroxide andmethyl ethyl ketone peroxide.

The miPP and optionally (A) and/or (B) may be dry-premixed ormelt-premixed and then melt-grafted or solution-grafted in a solvent.They may also be added separately in a device for placing in contact andblending (for example an extruder) with the grafting monomer and thefree-radical initiator. The usual devices of the thermoplastics industryfor mixing and blending may be used.

The amount of grafting monomer may be chosen in a suitable manner, butit is preferably from 0.01% to 10% and preferentially from 0.1% to 5%relative to the weight of the grafted composition of miPP optionallycomprising the polymer (A) and/or the polymer (B). The amount of graftedmonomer is determined by assaying the succinic functions by FTIRspectroscopy.

The invention also relates to a composition comprising miPP grafted andthen optionally diluted in at least one polyolefin (C1) and/or in atleast one polymer of elastomeric nature (D).

The polyolefin (C1) may be chosen from the polymers (A), (B) and miPP.

The polymer (D) is a polymer of elastomeric nature, that is to say thatit may-be:

-   -   (i) an elastomer within the meaning of ASTM D412, meaning that        it may be stretched at ambient temperature to twice its width,        maintained in this state for 5 minutes and then returned to        within 10% of its initial length when it is released; or    -   (ii) a polymer not having exactly the above characteristics, but        which may be stretched and returned substantially to its initial        length.

Advantageously, the MFI of (D) is between 0.1 and 50 g/10 min.

Examples of polymers (D) that may be mentioned include:

-   -   EPR (ethylene-propylene-rubber) and EPDM        (ethylene-propylene-diene);    -   polyethylenes obtained by metallocene catalysis, with a density        of less than 0.910 g/cm³;    -   polyethylenes of VLDPE type (very low density PE);    -   styrene elastomers such as SBR (styrene-butadiene-rubber),        styrene/butadiene/styrene (SBS) block copolymers,        styrene/ethylene/butene/styrene (SEBS) block copolymers and        styrene/isoprene/styrene (SIS) block copolymers;    -   copolymers of ethylene and of at least one unsaturated        carboxylic acid ester (already-defined above for (A));    -   copolymers of ethylene and of at least one vinyl ester of a        saturated carboxylic acid (already defined above for (A)).

The amount of (C1) and/or (D) is advantageously from 20 to 1 000 andpreferably 60 to 500 parts (by weight) per 10 parts of grafted miPP.Advantageously, (C1) and (D) are used. The preferred proportions aresuch that (D)/(C1) is between 0 and 1 and more particularly between 0and 0.5.

The composition according to the invention may be manufactured by theusual means of thermoplastics by melt-blending the various constituentsin BUSS twin-screw extruders, blenders or roll mills.

This composition may comprise various additives such as antioxidants,ultraviolet absorbers, antistatic agents, pigments, colorants,nucleating agents, fillers, glidants, lubricants, flame retardants andanti-blocking agents.

As regards the multilayer structure according to the invention, itcomprises a layer (L) comprising the composition according to theinvention and, directly attached thereto, a layer (E) that may be alayer (i) of oxygenated or nitrogenous polar resin, (ii) of a mineraloxide deposited on a polymer such as polyethylene (PE),polyethylene-terephthalate (PET) or ethylene/vinyl alcohol (EVOH)copolymer or (iii) a metallic or metalloplastic layer.

Examples of polar resins that are preferred in the layer (E) arepolyamide resins, an ethylene/saponified vinyl acetate or EVOHcopolymer, and polyesters.

More specifically, these polar resins comprise long-chain syntheticpolyamides containing amide-group structural units in the main chain,such as PA-6, PA-6,6, PA-6,10, PA-11 and PA-12; an ethylene/saponifiedvinyl acetate copolymer with a degree of saponification of about 90 to100 mol %, obtained by saponifying an ethylene/vinyl acetate copolymerwith an ethylene content from about 15 mol % to about 60 mol %;polyesters such as polyethylene terephthalate (PET), polybutyleneterephthalate (PBT), polyethylene naphthenate and blends of these polarresins.

The mineral oxide layer may be, for example, silica, deposited on alayer of PE, PET or EVOH. In this case, the structure according to theinvention thus comprises, successively: a binder layer comprising thecomposition according to the invention attached to a layer of SiO₂ (orSiO_(x)), which is itself deposited on a layer of PE, PET or EVOH.

The metallic layer may be, for example, a film or a sheet of a metalsuch as aluminium, iron, copper, tin or nickel, or an alloy containingat least one of these metals as major constituent. The thickness of thefilm or sheet is, for example, from about 0.01 to about 0.2 mm. It iscommon practice to degrease the surface of the metallic layer beforecoating it with the binder comprising the composition according to theinvention. This layer (E) may also be a metalloplastic layer such as,for example, an aluminium-coated PET sheet.

It would not constitute a departure from the context of the invention ifthe above structure was combined with other layers.

The invention also relates to the structure described above combined, onthe side remaining free of the binder layer (L), with a polyolefin-basedlayer (F), the binder layer thus allowing the layers (E) and (F) toadhere together. The structure defined herein is of the form layer(F)/layer (L)/layer (E). The polyolefin of the layer (F) may be chosenfrom the polymers (A) and (B) described above.

These structures are useful for making wrappings, for example rigidhollow bodies such as flasks, bottles, flexible bags or multilayerfilms.

The structures according to the invention are, for example, of the formbelow with the binder comprising the composition according to theinvention:

-   -   layer (F)/layer (L)/layer (E)/layer (L)/layer (F):        PE/binder/EVOH/binder/PE or PP/binder/EVOH/binder/PP    -   layer (F)/layer (L)/layer (E): PE/binder/EVOH or PE/binder/PA or        PP/binder/PA.

These structures and these wrappings may be manufactured by coextrusion,lamination, extrusion blow-moulding and coating.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The following preferred specific embodiments are,therefore, to be construed as merely illustrative, and not limitative ofthe remainder of the disclosure in any way whatsoever.

In the foregoing and in the following examples, all temperatures are setforth uncorrected in degrees Celsius and, all parts and percentages areby weight, unless otherwise indicated.

The entire disclosure(s) of all applications, patents and publications,cited above or below, and of corresponding French Application No.0110252, filed Jul. 31, 2001, is hereby incorporated by reference.

The products below were used to perform the tests and comparisons thatfollow:

miPP 1: miPP containing 3.5% ethylene, of density=0.900 g/cm³ and MFI 7g/10 min (at 230° C. under 2.16 kg).

miPP 2: miPP containing 3.5% ethylene, of density=0.900 g/cm³ and MFI=8g/10 min (at 230° C. under 2.16 kg).

miPP 3: miPP containing 5% ethylene, of density=0.900 g/cm³ and MFI=2.5g/10 min (at 230° C. under 2.16 kg).

PP 3060 MN 5: isotactic polypropylene containing propylene and ethyleneblocks, obtained by Ziegler-Natta catalysis (zniPP), of density=0.902g/cm³ and MFI=6 g/0.10 min (at 230° C. under 2.16 kg).

PP 3020 GN3: random polypropylene copolymer obtained by Ziegler-Nattacatalysis (zniPP), of density=0.900 g/cm³ and MVI (Melt Volume Index)=2cm³/10 min (at 230° C. under 2.16 kg).

MAH: maleic anhydride.

LLDPE: linear low density polyethylene, of density=0.900 g/cm³ and MFI=3g/10 min (at 190° C. under 2.16 kg).

The products are manufactured in a Leistritz co-rotary twin-screwextruder and grafted with maleic anhydride.

The extruder comprises eight zones referred to as Z1 to Z8, zone Z8being at the end of the extruder on the outlet side of the graftedproducts. The process is performed at usual temperatures known to thoseskilled in the art.

The maleic anhydride, on polyethylene powder, and the polypropylene tobe grafted are introduced into zone Z1 via two separate weight-meteringdevices.

The free-radical initiator, in pure form or diluted in a suitablesolvent, is introduced via a metering pump into zone Z2. Thetemperatures in zones Z3, Z4 and Z5 are at least sufficient for 99.9% ofthe free-radical initiator to react before zone Z6. The initiator usedis 2,5-dimethyl-2,5-(di-tert-butyl)hexane peroxide or DHBP (Luperox®101). The residues of the free-radical initiator, the solvent and theunreacted maleic anhydride are degassed under vacuum in zone Z6.

The extrusion flow rate leaving the zone Z8 varies according to thescrew speed, set between 12 and 15 kg/h. The extrudate is granulatedafter cooling.

Table 1 collates the results of the grafting of miPP with MAH forExamples Ex2, Ex3 and Ex4 and of zniPP with MAH for the comparative Cp1.All the percentages are on a weight basis and the weight percentages ofMAH and of initiator are relative to 100% of miPP or zniPP, depending onthe case.

It is found that, for the grafted zniPP (Comparative Cp1), the MFIobtained is 13.5 g/10 min, whereas it remains less than or equal to 10g/10 min for the examples of grafted miPP according to the invention(Ex2, Ex3 and Ex4) for a virtually equivalent percentage of grafted MAH.

A five-layer structure consisting successively and respectively ofPP/binder/EVOH/binder/PP, in which:

-   -   PP denotes a layer of isotactic polypropylene obtained by        Ziegler-Natta catalysis (zniPP),    -   binder denotes a layer comprising the composition defined in        Table 2, and    -   EVOH denotes a layer of ethylene/vinyl alcohol copolymer,        was then produced by cast technology.

The thickness of the successive layers is, respectively, in μm:20/10/10/10/50.

The peel force between the 20-μm PP layer and the 10-μm binder layer wasthen measured. The binder compositions in weight percentages, the peelforces (expressed in N/15 mm at a pulling speed of 200 mm/min) at timest=0 (immediately after producing the structure) and t=8 days (8 daysafter producing the structure) and the standard deviations (s) are givenin Table 2.

It is found that the binder compositions comprising grafted miPP givesbetter adhesion results than the binder compositions comprising graftedzniPP instead of grafted miPP.

TABLE 1 MAH introduced DHBP introduced MFI in g/10 min (at % MAH graftedPP (%) (%) (%) 190° C. under 325 g) after stoving Cp1 PP3060 MN 5 1001.8 0.1600 13.5 0.58 Ex2 miPP 1 100 1.8 0.1600 8.4 0.49 Ex3 miPP 2 1001.8 0.1600 7.5 0.55 Ex4 miPP 3 100 1.8 0.1600 10 0.53

TABLE 2 BINDER composition Peel force at Peel force at zniPP PE t = 0days s at t = 0 t = 8 days s at (C1) (%) (D) (%) MAH grafted PP (%)(N/15 mm) days (N/15 mm) t = 8 days Ex5 PP 3020GN3 57 LLDPE 18 miPP1* 252.7 0.22 5.19 0.21 Ex6 PP 3020GN3 57 LLDPE 18 miPP2** 25 3.54 0.29 5.640.24 Ex7 PP 3020GN3 57 LLDPE 18 miPP3*** 25 4.11 0.1 5.85 0.12 Cp8 PP3020GN3 57 LLDPE 18 PP3060 MN5**** 25 2.27 0.13 4.22 0.21 *grafted miPPobtained in Ex2; **grafted miPP obtained in Ex3; ***grafted miPPobtained in Ex4; ****grafted zniPP obtained in Cp1.

The preceding examples can be repeated with similar success bysubstituting the generically or specifically described reactants and/oroperating conditions of this invention for those used in the precedingexamples. From the foregoing description, one skilled in the art caneasily ascertain the essential characteristics of this invention and,without departing from the spirit and scope thereof, can make variouschanges and modifications of the invention to adapt it to various usagesand conditions.

1. A multilayer structure comprising a layer (L) containing acomposition comprising 10% to 100% by weight of isotactic polypropylenehomopolymer or copolymer obtained by metallocene catalysis (miPP); 0% to90% by weight of polyethylene (A) homopolymer or copolymer; 0% to 90% byweight of polymer (B) selected from the group consisting of isotacticpolypropylene homopolymer or copolymer obtained by Ziegler-Nattacatalysis (B1), poly-(1-butene)homopolymer or copolymer (B2),polystyrene homopolymer or copolymer (B3), a blend of (B1) and (B2), ablend of (B1) and (B3), a blend of (B2) and (B3), and a blend of (B1),(B2) and (3); the percentages beina based on the total weight of theisotactic polymer (miPP) and any polymer (A) and polymer (B); and saidpolymer or polymers being grafted with a functionalised monomer; and,directly attached to said layer (L), a layer (E), which is polar,nitrogenous or oxygenated, a mineral oxide deposited on a polymer, ormetallic or meralloplastic.
 2. The multilayer structure according toclaim 1, wherein the functionalised monomer is unsaturated andnon-aromatic.
 3. The multilayer structure according to claim 1, whereinthe functionalised monomer is selected from the group consisting ofalkoxysilanes, carboxylic acids, acid chlorides, isocyanates,oxazolines, epoxides, amines and hydroxides.
 4. The multilayer structureaccording to claim 1, wherein the functionalised monomer is maleicanhydride.
 5. The multilayer structure according to claim 1, comprisingpolyethylene homopolymer or polyethylene (A) copolymer having at leastone comonomer selected from the group consisting of α-olefins containing3 to 30 carbon atoms, esters of unsaturated carboxylic acids, vinylesters of saturated carboxylic acids, unsaturated epoxides, alicyclicglycidyl esters and ethers, unsaturated carboxylic acids, salts thereof,anhydrides thereof, and dienes.
 6. The multilayer structure according toclaim 1, comprising polyethylene (A) selected from the group consistingof LDPE, HDPE, LLDPE, VLDPE, PE obtained by metallocene catalysis, EPRand EPDM elastomers and blends thereof, ethylene/alkyl (meth)acrylatecopolymers, ethylene/alkyl (meth)acrylate/maleic anhydride copolymersand ethylene/vinyl acetate/maleic anhydride copolymers.
 7. Themultilayer structure according to claim 1, said layer (L) furthercomprising a polyolefin (C1) and/or a polymer of elastomeric nature (D).8. The multilayer structure according to claim 7, wherein the amount ofpolyolefin (C1) and/or of polymer of elastomeric nature (D) is 20 to1,000 parts by weight per 10 parts of grafted isotactic polypropyleneobtained by metallocene catalysis.
 9. The multilayer structure accordingto claim 7, wherein the proportions of polyolefin (C1) and of polymer ofelastomeric nature (D) are such that the radio (D)/(C1) is between 0and
 1. 10. The multilayer structure according to claim 1, furthercomprising coextrusion binder.
 11. A multilayer structure according toclaim 1, wherein layer (E) is a layer of polyamide resin, ofethylene/saponified vinyl acetate (EVOH) copolymer or of polyester. 12.A multilayer structure according to claim 11, wherein layer (E) is amineral oxide deposited on PE, polyethylene terephthalate (PET) or(EVOH).
 13. A structure according to claim 1, comprising apolyolefin-based layer (F) directly attached to the layer (L), the layer(L) thus being sandwiched between the said layer (F) and the layer (E).14. A wrapping or a rigid hollow body or flexible container, comprisinga structure as claimed in claim
 1. 15. A multilayer structure comprisinga layer (L) containing a composition comprising: 10% to 100% by weightof isotactic polypropylene homopolymer or copolymer obtained bymetallocene catalysis (miPP) said isotactic polypropylene copolymercomprising not more than 10% of a comonomer selected from the groupconsisting of ethylene, butene, isobutylene, 4-methyl pentene, andmixtures thereof; 0% to 90% by weight of polyethylene (A) homopolymer orcopolymer; 0% to 90% by weight of polymer (B) selected from the groupconsisting of isotactic polypropylene homopolymer or copolymer obtainedby Ziegler-Natta catalysis (B1), poly-(1-butene)homopolymer or copolymer(B2), polystyrene homopolymer or copolymer (B3), a blend of (B1) and(B2), a blend of (B1) and (B3), a blend of (B2) and (B3), and a blend of(B1), (B2), and (B3); the percentages being based on the total weight ofthe isotactic polymer (miPP) and any polymer (A) and polymer (B); andsaid polymer or polymers being grafted with a functionalised monomer,and directly attached to said layer (L), a layer (E), which is polar,nitrogenous or oxygenated, a mineral oxide deposited on a polymer, ormetallic or metalloplastic.
 16. The multilayer structure according toclaim 15, wherein the functionalised monomer is unsaturated andnon-aromatic.
 17. The multilayer structure according to claim 15,wherein the functionalised monomer is selected from the group consistingof alkoxysilanes, carboxylic acids, acid chlorides, isocyanates,oxazolines, epoxides, amines and hydroxides.
 18. The multilayerstructure according to claim 15, wherein the functionalised monomer ismaleic anhydride.
 19. The multilayer structure according to claim 15,comprising polyethylene homopolymer or polyethylene (A) copolymer havingat least one comonomer selected from the group consisting of α-olefinscontaining 3 to 30 carbon atoms, esters of unsaturated carboxylic acids,vinyl esters of saturated carboxylic acids, unsaturated epoxides,alicyclic glycidyl esters and ethers, unsaturated carboxylic acids,salts thereof, anhydrides thereof, and dienes.
 20. Themultilayer-structure according to claim 15, comprising polyethylene (A)selected from the group consisting of LDPE, HDPE, LLDPE, VLDPE, PEobtained by metallocene catalysis, EPF and EPDM elastomers and blendsthereof, ethylene/alkyl (meth)acrylate copolymers, ethylene/alkyl(meth)acrylate/maleic anhydride copolymers and ethylene/vinylacetate/maleic anhydride copolymers.
 21. The multilayer-structureaccording to claim 15, said layer (L) further comprising a polyolefin(C1) and/or a polymer of elastomeric nature (D).
 22. The multilayerstructure according to claim 21, wherein the amount of polyolefin (C1)and/or of polymer of elastomeric nature (D) is 20 to 1,000 parts byweight per 10 parts of grafted isotactic polypropylene obtained bymetallocene catalysis.
 23. The multilayer structure according to claim21, wherein the proportions of polyolefin (C1) and of polymer ofelastomeric nature (D) are such that the ratio (D)/(C1) is between 0and
 1. 24. The multilayer structure according to claim 15, furthercomprising coextrusion binder.
 25. A multilayer structure according toclaim 15, wherein layer (E) is a layer of polyamide resin, ofethylene/saponified vinyl acetate (EVOH)copolymer or of polyester.
 26. Amultilayer structure according to claim 25, wherein layer (E) is amineral oxide deposited on PE, polyethylene terephthalate (PET) or(EVOH).
 27. A structure according to claim 15, comprising apolyolefin-based layer (F) directly attached to the layer (L), the layer(L) thus being sandwiched between the said layer (F) and the layer (E).28. A wrapping or a rigid hollow body or flexible container, comprisinga structure as claimed in claim
 15. 29. A multilayer structure accordingto claim 15, comprising polymer (B) in layer (L).
 30. A multilayerstructure according to claim 15, comprising both (A) and (B) in layer(L).
 31. A multilayer structure comprising a layer (L) containing acomposition comprising: 10% to 100% by weight of isotactic polypropylenehomopolymer or copolymer obtained by metallocene catalysis (miPP); 0% to90% by weight of polyethylene (A) homopolymer or copolymer; 0% to 90% byweight of polymer (B) selected from the group consisting of isotacticpolypropylene homopolymer or copolymer obtained by Ziegler-Nattacatalysis (B1), poly-1(butene)homopolymer or copolymer (B2), polystyrenehomopolymer or copolymer (B3), a blend of (B1) and (B2), a blend of (B1)and (B3), a blend of (B2) and (B3), and a blend of (B1), (B2), and (B3);the percentages being based on the total weight of the isotactic polymer(miPP) and any polymer (A) and polymer (B); and said polymer or polymersbeing grafted with a functionalised monomer, and wherein saidcomposition is diluted in a polyolefin (C1) and/or a polymer ofelastomeric nature (D), and directly attached to said layer (L), a layer(E), which is polar, nitrogenous or oxygenated, a mineral oxidedeposited on a polymer, or metallic or metalloplastic.
 32. Themultilayer structure according to claim 31, wherein the amount ofpolyolefin (C1) and/or of polymer of elastomeric nature (D) is 20 to1,000 parts by weight per 10 parts of grafted isotactic polypropyleneobtained by metallocene catalysis.
 33. The multilayer structureaccording to claim 31, wherein the proportions of polyolefin (C1) and ofpolymer of elastomeric nature (D) are such that the ratio (D)/(C1) isbetween 0 and
 1. 34. The multilayer structure according to claim 21,wherein the amount of polyolefin (C1) and/or of polymer of elastomericnature (D) is 20 to 1,000 parts by weight per 10 parts of graftedisotactic polypropylene obtained by metallocene catalysis, and saidcomposition further comprising a coextrusion binder.